The present invention relates to a lapping sensor used in a height adjustment of a magnetoresistive effect (MR) film (MR-height adjustment) when a magnetic head with an MR element is fabricated, and to a lapping control method using the lapping sensor.
In the MR-height adjustment process, MR heights of a plurality of MR elements are adjusted in one operation by polishing one surface (ABS, Air Bearing Surface) of a bar or block obtained by cutting a wafer so that a plurality of magnetic heads with the MR elements are aligned along the bar. In order to precisely and equally adjust MR heights of MR elements in one bar and MR heights of MR elements in bars, a lapping amount is controlled in response to electrical signals from a plurality of lapping sensors each called ELG (Electric Lapping Guide) or RLG (Resistance Lapping Guide), which are in general formed in each bar for detecting the lapped height of the bar. Bending of the bar may be additionally controlled in response to the electrical signals.
The ELG or RLG is substantially configured by a resistor film formed adjacent to and in line with the ABS to be lapped, and by a pair of connection pads electrically connected with both end sections of the resistor film. When lapping the MR height, the resistor film will be also lapped to decrease its height and to increase its electrical resistance. Thus, the lapped amount can be obtained from the change in a terminal voltage of the resistor film.
Such lapping sensors are disclosed in for example U.S. Pat. Nos. 5,065,483, 5,210,667, 5,242,524, 5,361,547, 5,997,381, 6,007,405 and 6,03,849.
In general, the pair of the connection pads for taking out the electrical signal from the resistor film of the lapping sensor are arranged on an element-forming surface of the bar side by side with terminal electrodes of magnetic heads.
FIG. 1 shows a plane view schematically illustrating an element-forming surface of a part of a conventional bar obtained by cutting in lines an wafer on which many magnetic heads are formed in matrix.
In the figure, reference numerals 10 denote magnetic head sections, and 11 denote lapping sensor sections adjacent to the respective magnetic head sections 10. On the element-forming surface of each magnetic head section 10, four magnetic head connection pads 13a-13d electrically connected to a composite magnetic head element 12 consisting of an MR element and an inductive element are formed. On the element-forming surface of each lapping sensor section 11, two resistor-film connection pads 14a and 14b electrically connected to the resistor film, for extracting an electrical signal from the resistor film are aligned perpendicular to a surface to be lapped (lapping surface) 15 of the bar.
Such conventional structure had been applicable to a 30% magnetic head slider with a size of 1.0 mmxc3x971.235 mmxc3x970.3 mm. However, in case of a magnetic head slider with a size smaller than that of the 30% slider such as a 20% slider of 0.7 mmxc3x970.85 mmxc3x970.23 mm, since the space between the upper connection pad 14a and the lower connection pad 14b and also the space between the lower connection pad 14b and the lapping surface 15 became extremely narrow, the following problem had been occurred.
In the lapping control process, one end terminals of a printed circuit board (PCB) with the other end terminals to be electrically connected to a lapping control device are electrically connected to the resistor-film connection pads 14a and 14b by wires in general. If these spaces are too narrow, because a wire bonding machine has a limited accuracy in bonding, a wire 16 bonded to the lower connection pad 14b may come into contact with the upper connection pad 14a as shown in FIG. 2 causing a short circuit to occur, or a wire 17 bonded to the lower connection pad 14b may come into contact with a lapping plate touched with the lapping surface 15 as shown in FIG. 2
If the resistor-film connection pads 14a and 14b are short-circuited by the wire 16, the measured resistance of the lapping sensor will become lower than its actual resistance and thus an excess lapping may be occurred. Also, if the wire 17 touches the lapping plate, noises may be mixed in the measured signal due to current flowing into the lapping plate via the wire 17. Then, a correct resistance of the lapping sensor cannot be measured and a correct lapping cannot be expected.
In order to solve such problem, there may be an arrangement in which resistor-film connection pads 34a and 34b of the lapping sensor are aligned in parallel with a lapped surface 35 of a bar by forming the connection pad 34a over a lapping sensor section 31 and a magnetic head section 30 as shown in FIG. 3. However, this arrangement will make the layout design of magnetic head connection pads very difficult and also will expose the section of the resistor-film connection pad 34a when the magnetic head section 30 is separated by cutting from the section 31.
There may be another arrangement in which resistor-film connection pads 44a and 44b of one lapping sensor are aligned in parallel with a surface to be lapped 45 of a bar by forming the connection pad 44a in one lapping sensor section 41 and by forming the other connection pad 44b in another lapping sensor section 41 as shown in FIG. 4. However, this arrangement will make the resistance of the lapping sensor to increase because of a long lead conductor 48 for connecting the resistor film of the lapping sensor with the connection pad 44b, and also will expose the section of the lead line 48 when the magnetic head section 40 is separated by cutting from the lapping sensor section 41.
It is therefore an object of the present invention to provide a lapping sensor which can surely and stably detect a correct lapping amount even when a magnetic head slider is to be fabricated is downsized.
Another object of the present invention is to provide a lapping control method using a lapping sensor, whereby an MR height can be surely and stably adjusted to a correct value.
According to the present invention, a lapping sensor used in fabrication of a magnetic head with an MR element includes a resistor film with a resistance that varies depending upon a lapping amount, and a pair of connection pads formed on a element-forming surface of the magnetic head and electrically connected to both end sections of the resistor film. The pair of connection pads consist of a first connection pad and a second connection pad located nearer to a lapping surface than the first connection pad. One edge of the first connection pad is faced to one edge of the second connection pad and inclined toward the lapping surface.
One edge of the first connection pad formed far side from the lapping surface (upper connection pad) is faced to one edge of the second connection pad formed near side from the lapping surface (lower connection pad) and inclined toward the lapping surface. Thus, when wires are bonded to these connection pads, contact of the wire bonded to the lower connection pad with the upper connection pad can be prevented. Namely, by routing the wire bonded to the lower connection pad run along the inclined edge of the upper connection pad, a possibility of contact of this wire with the upper connection pad can be extremely reduced. As a result, a correct lapping amount can be always provided, and therefore an MR height can be surely and stably adjusted to a correct value even when a magnetic head slider to be fabricated is downsized.
It is preferred that the one edge of the first connection pad (upper connection pad) has a linear shape. In this case, more preferably, the one edge of the second connection pad (lower connection pad) has also a linear shape parallel to the one edge of the first connection pad (upper connection pad). Thus, the space between the upper connection pad and the lower connection pad and the space between the lower connection pad and the lapping surface can be widened. Therefore, a possibility of contact of the wire boned to the lower connection pad with the upper connection pad and/or a possibility of contact of this wire with a lapping plate abutted to the lapping surface can be extremely reduced. As a result, a correct lapping amount can be always provided even when a magnetic head slider to be fabricated is downsized.
It is also preferred that each of the first and second connection pads is formed in a triangular shape, and that each of the one edge of the first connection pad and the one edge of the second connection pad corresponds to an oblique side of the triangular shape. In this case, more preferably, the triangular shape is a right triangular shape.
It is preferred that the one edge of the first connection pad has a curved shape. In this case, it is more preferred that each of the first and second connection pads is formed in a circular or oval shape.
It is also preferred that the first and second connection pads are aligned along a direction perpendicular to or inclined toward the lapping surface.
According to the present invention, furthermore, a lapping control method using at least one lapping sensor for fabricating a magnetic head with an MR element includes a step of preparing at least one the aforementioned lapping sensor, a step of connecting bonding wires to the first and second connection pads, respectively so that the bonding wires run along the one edge of the first connection pad, and a step of extracting an electrical signal from the at least one lapping sensor to control the lapped amount.
It is preferred that the method further includes a step of adjusting a height of an MR film in the MR element in accordance with the electrical signal extracted.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.